1. Field of the Invention
The present invention relates to an organic light emitting device. More particularly, the present invention relates to an organic light emitting device that emits white light.
2. Discussion of the Related Art
An organic light emitting device has a structure in which an organic light emitting portion is formed between a cathode and an anode, wherein electrons are injected into the cathode, and holes are injected into the anode. If the electrons generated in the cathode and the holes generated in the anode are injected into the organic light emitting portion, an exciton is generated by combination of the injected electrons and holes, and then the generated exciton is transited from the excited state to a ground state, whereby light is emitted.
Such an organic light emitting device may be applied as a back light of a liquid crystal display device or a display device itself as well as lighting. Particularly, an organic light emitting device that emits white light may be applied to a full color display device by combination with a color filter.
In a case of a full color display device obtained by combination of a color filter and a white organic light emitting device, because the organic light emitting device emitting white light may be manufactured by one deposition process for each pixel, it is advantageous in that the process may be performed without a shadow mask.
Hereinafter, an organic light emitting device emitting white light according to the related art will be described with reference to the accompanying drawing.
FIG. 1 is a brief cross-sectional view illustrating an organic light emitting device according to one embodiment of the related art.
As shown in FIG. 1, the organic light emitting device according to one embodiment of the related art includes an anode 1, a first stack 2, an intermediate layer 3, a second stack 4, and a cathode 5.
The first stack 2 is formed on the anode 1 to emit blue (B) light. Although not shown in detail, the first stack 2 includes a light emitting layer emitting blue (B) light, a hole transporting layer for transporting holes to the light emitting layer, and an electron transporting layer for transporting electrons to the light emitting layer.
The intermediate layer 3 is formed between the first stack 2 and the second stack 4 and serves to uniformly control charges between the first stack 2 and the second stack 4. This intermediate layer 3 includes an N type charge generating layer 3a providing electrons to the first stack 2 and a P type charge generating layer 3b providing holes to the second stack 4.
The N type charge generating layer 3a is made of an organic material doped with Li having electron injection or electron transporting characteristic, and the P type charge generating layer 3b is made of an organic material having hole injection characteristic or hole transporting characteristic.
The second stack 4 is formed on the intermediate layer 3 to emit yellow green (YG) light. Similar to the first stack 2, the second stack 4 includes a light emitting layer for emitting yellow green (YG) light, a hole transporting layer for transporting holes to the light emitting layer, and an electron transporting layer for transporting electrons to the light emitting layer.
The aforementioned organic light emitting device according to one embodiment of the related art emits white light by mixing blue light emitted from the first stack 2 with yellow green light emitted from the second stack 4.
However, in the aforementioned organic light emitting device according to the embodiments of the related art, because the N type charge generating layer 3a and the P type charge generating layer 3b, which constitute the intermediate layer 3, are formed by a separate deposition process and the hole transporting layer constituting the second stack 4 on the intermediate layer 3 is also formed by a separate deposition process, a problem occurs in that the number of depositions and the number of processes are increased, whereby a driving voltage is increased.